The present embodiments relate to human body representation systems. An adult human body has 206 bones, more than 600 skeletal muscles, and a divergent fat tissue distribution throughout the population, making the human body a complex object to model effectively and efficiently. Nonetheless, such a representation is becoming increasingly more desirable due to emerging applications in medical scanning, computer vision, computer graphics, and human-computer interaction.
While analyzing the exterior form (i.e. body pose and shape) of the human body, it is beneficial to consider the underlying structures that are responsible for creating the exterior form. This anatomical perspective common in modeling the human body is an articulated skeleton supporting several layers of deformable tissue including muscles, fat tissue, and skin. Each of these components is modeled and incorporated in various ways to obtain a representation that accounts for the variations in body pose and shape.
Anatomy-inspired geometric body models are one approach. Every anatomical component (e.g., the skeleton, muscles, fat, and tissue) is represented using geometric models. The goal is to have a very realistic representation of the human body, so that realistic instances may be synthesized with various poses and shapes. These methods are usually employed for computer animation applications, where the efficiency may be sacrificed in order to achieve more visually pleasing instances. In one example, most of the bones and the muscles in the upper body are modeled, resulting in a representation with 68 bones (147 degrees-of-freedom) and 814 skeletal muscles where each muscle is modeled using a piecewise line segment model (i.e., an idealization of the musculature). A physics-based soft tissue model creates a high quality skin surface. Such a model is expected to synthesize very realistic instances, but the skeletal system has more than a hundred degrees-of-freedom and the muscle system has hundreds of additional parameters to control. Hence, using such a model in a fitting scenario is not very feasible.
Another approach used for fitting is a data-drive body model, such as shape completion and animation of people (SCARE). For most non-graphics applications, a more simply or sufficiently complex skeletal system (e.g., 15-20 rigid parts) may still be represented geometrically. Rather than using a geometric representation of the deformable tissue, a data-driven method models the layers of deformable tissue. This decouples the deformations due to pose (e.g., orientation of bones or skeleton) from the deformations due to shape (i.e. person-specific size and other characteristics) and represents each separately. The skeleton parts are rigid or fixed in characteristics other than orientation, allowing for solution for orientation. Differently, the shape deformations are modeled using a linear subspace, allowing for patient specific variation. Therefore, the shape spaces cover all person-specific body shape deformations, both due to the changes in the skeletal system and the deformable tissue. Even though this is an intuitive representation, the shape space is limited due to the amount of variation handled.